HFCs are of particular interest as potential replacements for highly useful chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). Unlike CFCs and HCFCs, HFCs do not contain chlorine and therefore do not decompose to form chlorine-containing chemical species, which are suspected of causing depletion of the ozone layer. While HFCs thus avoid the main disadvantage of such chlorine-containing compounds, they nevertheless possess many of the beneficial properties of those compounds. For example, HFCs have been used successfully in place of HCFCs and CFCs as heat transfer agents, blowing agents, and propellants. Thus, HFCs are desirable targets of chemical synthesis.
Known methods for forming HFC's generally use as starting materials halogenated alkanes and alkenes, such as, for example, vinylidene chloride, carbon tetrachloride and perchloroethylene. For example, U.S. Pat. No. 5,574,192--Van Der Puy et al discloses a method of making 1,1,1,3,3-pentafluoropropane (HFC-245fa) in which vinyl chloride is reacted with carbon tetrachloride and then fluorinated to produce the desired HFC. U.S. Pat. No. 5,728,904--Van Der Puy et al discloses a three-step method of reacting carbon tetrachloride with vinylidene chloride, fluorinating and then reducing to make the desired HFC.
The present inventors have come to appreciate that such prior processes are disadvantageous for several reasons. One such disadvantage is that the availability of many halogenated compounds, such as carbon tetrachloride, is limited and their use as starting materials tends to be very expensive. Another disadvantage is that these prior art processes are not flexible and produce HFC-245fa as the sole product. No useful intermediates or by-products are co-produced. Thus, the HFC-245fa produced by the prior art processes have relatively high operating costs, as well as relatively high capital costs.
Recognizing these and other drawbacks of the prior art, the present inventors have perceived a need for a new, efficient and more desirable method for producing a wide range of HFCs. These and other objects are achieved by the present invention as described below.